/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingComponents/Public/Selection/ToolSelectionUtil.h
Add the geometry selection elements corresponding to the given Selection to Elements. This function does not reset Elements before adding elements. If the Selection has Polygroup topology then use the given Topology to accumulate elements if it isn't null, otherwise compute a FGroupTopology from SourceMesh.TriangleGroups and use that to accumulate elements. If the Selection has Triangle topology then the Topology argument is ignored. Return false if there was an error and true otherwise
namespace ToolSelectionUtil { bool ToolSelectionUtil::AccumulateSelectionElements ( [UE::Geometry::FGeometrySelectionElements](API\Plugins\DynamicMesh\Selections\FGeometrySelectionElements) & Elements, const [UE::Geometry::FGeometrySelection](API\Plugins\DynamicMesh\Selections\FGeometrySelection) & Selection, const [UE::Geometry::FDynamicMesh3](API\Runtime\GeometryCore\DynamicMesh\FDynamicMesh3) & SourceMesh, const [UE::Geometry::FGroupTopology](API\Plugins\DynamicMesh\FGroupTopology) * Topology, const FTransform * ApplyTransform, bool bMapFacesToEdges ) }